Revert "x86/ftrace: Use alternative RET encoding"

Revert "x86/ftrace: Use alternative RET encoding"

This reverts commit e54fcb0812faebd147de72bd37ad87cc4951c68c.

This temporarily reverts the backport of upstream commit
1f001e9da6bbf482311e45e48f53c2bd2179e59c. It was not correct to copy the
ftrace stub as it would contain a relative jump to the return thunk which
would not apply to the context where it was being copied to, leading to
ftrace support to be broken.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>